Speech recognition using device docking context

ABSTRACT

Methods, systems, and apparatuses, including computer programs encoded on a computer storage medium, for performing speech recognition using dock context. In one aspect, a method includes accessing audio data that includes encoded speech. Information that indicates a docking context of a client device is accessed, the docking context being associated with the audio data. A plurality of language models is identified. At least one of the plurality of language models is selected based on the docking context. Speech recognition is performed on the audio data using the selected language model to identify a transcription for a portion of the audio data.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.61/435,022, filed on Jan. 21, 2011 and U.S. Utility application Ser. No.13/040,553 filed Mar. 4, 2011. The entire contents of these applicationsare incorporated herein by reference.

BACKGROUND

The use of speech recognition is becoming more and more common. Astechnology has advanced, users of computing devices have gainedincreased access to speech recognition functionality. Many users rely onspeech recognition in their professions and in other aspects of dailylife.

SUMMARY

In a general aspect, a computer-implemented method includes accessingaudio data that includes encoded speech; accessing information thatindicates a docking context of a client device, the docking contextbeing associated with the audio data; identifying a plurality oflanguage models; selecting at least one of the plurality of languagemodels based on the docking context; and performing speech recognitionon the audio data using the selected language model to identify atranscription for a portion of the audio data.

Implementations may include one or more of the following features. Forexample, the information that indicates a docking context of the clientdevice indicates a connection between the client device and a seconddevice with which the client device is physically connected. Theinformation that indicates a docking context of the client deviceindicates a connection between the client device and a second devicewith which the client device is wirelessly connected. The methodincludes determining, for each of the plurality of language models, aweighting value to assign to the language model based on the dockingcontext, the weighting value indicating a probability that the languagemodel will indicate a correct transcription for the encoded speech,where selecting at least one of the plurality of language models basedon the docking context includes selecting at least one of the pluralityof language models based on the assigned weighting values. The speechencoded in the audio data was detected by the client device, and theinformation that indicates a docking context indicates whether theclient device was connected to a docking station while the speechencoded in the audio data was detected by the client device. The speechencoded in the audio data was detected by the client device, and theinformation that indicates a docking context indicates a type of dockingstation to which the client device was connected while the speechencoded in the audio data was detected by the client device. The encodedspeech includes one or more spoken query terms, the transcriptionincludes a transcription of the spoken query terms, and the methodfurther includes causing a search engine to perform a search using thetranscription of the one or more spoken query terms and providinginformation indicating the results of the search to the client device.Determining weighting values for each of the plurality of languagemodels includes accessing stored weighting values associated with thedocking context. Determining weighting values for each of the pluralityof language models includes accessing stored weighting values andaltering the stored weighting values based on the docking context. Eachof the plurality of language models is trained for a particular topicalcategory of words. Determining a weighting value based on the dockingcontext includes determining that the client device is connected to avehicle docking station and determining, for a navigation language modeltrained to output addresses, a weighting value that increases theprobability that the navigation language model is selected relative tothe other language models in the plurality of language models.

In another general aspect, a computer-implemented method includesdetecting audio containing speech at a client device; encoding thedetected audio as audio data; transmitting the audio data to a serversystem; identifying a docking context of the device; transmittinginformation indicating the docking context to the server system; andreceiving a transcription of at least a portion of the audio data at theclient device, the server system having selected a language model from aplurality of language models based on the information indicating thedocking context, generated the transcription by performing speechrecognition on the audio data using the selected language model, andtransmitted the transcription to the client device.

Implementations may include one or more of the following features. Forexample, the identified docking context is the docking context of theclient device at the time the audio is detected. The informationindicating a docking context of the client device indicates a connectionbetween the client device and a second device with which the clientdevice is physically connected. The information indicating a dockingcontext of the client device indicates a connection between the clientdevice and a second device with which the client device is wirelesslyconnected.

Other implementations of these aspects include corresponding systems,apparatus, and computer programs, configured to perform the actions ofthe methods, encoded on computer storage devices.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features andadvantages will become apparent from the description, the drawings, andthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a system for performingspeech recognition using a docking context of a client device.

FIG. 2A is a diagram illustrating an example of a representation of alanguage model.

FIG. 2B is a diagram illustrating an example of a use of an acousticmodel with the language model illustrated in FIG. 2A.

FIG. 3 is a flow diagram illustrating an example of a process forperforming speech recognition using a docking context of a clientdevice.

FIG. 4 is a block diagram of computing devices.

DETAILED DESCRIPTION

In various implementations, the docking context of a client device canbe used to improve the accuracy of speech recognition. A speechrecognition system can include multiple language models, each trainedfor a different topic or category of words. When accessing audio datathat includes encoded speech, the speech recognition can also accessinformation indicating a docking context associated with the speech. Thedocking context can include, for example, the docking context of adevice that detected the speech, at the time the speech was detected.The speech recognition system can use the docking context to select aparticular language model to use for recognizing the speech entered inthat docking context.

In many instances, the docking context of a device can indicate the typeof speech that a user of the device is likely to speak while the deviceis in that docking context. For example, a user speaking into a clientdevice connected to a car docking station is likely to use words relatedto navigation or addresses. When speech is entered on a device in avehicle docking station, the speech recognition system can select alanguage model trained for navigation-related words and use it torecognize the speech. By selecting a particular language model based onthe docking context, the speech recognition system can bias the speechrecognition process toward words most likely to have been spoken in thatdocking context. As a result, speech recognition using a language modelselected based on docking context can yield a transcription that is moreaccurate than speech recognition using a generalized language model.

FIG. 1 is a diagram illustrating an example of a system 100 forperforming speech recognition using a docking context of a client device102. The system 100 includes a client communication device (“clientdevice”) 102, a speech recognition system 104 (e.g., an Automated SpeechRecognition (“ASR”) engine), and a search engine system 109. The clientdevice 102, the speech recognition system 104, and the search enginesystem 109 communicate with each other over one or more networks 108.FIG. 1 also illustrates a flow of data during states (A) to (G).

The client device 102 can be a mobile device, such as a cellular phoneor smart phone. Other examples of client device 102 include GlobalPositioning System (GPS) navigation systems, tablet computers, notebookcomputers, and desktop computers.

The client device 102 can be connected to a docking station 106. Thedocking station 106 can be physically coupled to the client device 102and can communicate with the client device 102, for example, to transferpower and/or data, over a wired or wireless link. The docking station106 can physically hold or stabilize the client device 102 (e.g., in acradle or holster) while the client device 102 communicates with thedocking station 106. The client device 102 can be directly connected tothe docking station 106 or can be connected through a cable or otherinterface.

During state (A), a user 101 of the client device 102 speaks one or moreterms into a microphone of the client device 102. In the illustratedexample, the user 101 speaks the terms 103 (“10 Main Street”) as part ofa search query. Utterances that correspond to the spoken terms 103 areencoded as audio data 105. The terms 103 can be identified as queryterms based on, for example, a search interface displayed on the clientdevice 102, or a search control selected on the user interface of theclient device 102.

The client device 102 also identifies a docking context, for example,the docking context of the client device 102 when the user 101 speaksthe terms 103. In the illustrated example, the client device 102 isconnected to a car docking station 106 when the user 101 speaks theterms 103. The client device 102 determines, for example, that theclient device 102 is connected to the docking station 106 (e.g., theclient device 102 is currently “docked”), that the docking station 106is a vehicle docking station, and that the docking station 106 ispowered on.

The docking context can be the context in which the terms 103 werespoken. For example, the docking context can include the state of theclient device 102 at the time the audio corresponding to the spokenquery terms 103 was detected by the client device 102. Detecting speechcan include, but is not limited to, sensing, receiving, or recordingspeech. Detecting speech may not require determining that received audiocontains speech or identifying a portion of audio that includes encodedspeech, although these may occur in some implementations.

The docking context can include the identity and characteristics of thedocking station to which the client device 102 is connected. Forexample, the docking context can include one or more of (i) whether ornot the client device 102 is connected to any docking station 106, (ii)the type of docking station 106 to which the client device 102 isconnected (e.g., vehicle docking station, computer, or music player),(iii) the operating state of the docking station 106 (e.g., whether thedocking station 106 is on, off, idle, or in a power saving mode), and(iv) the relationship between the client device 102 and the dockingstation 106 (e.g., client device 102 is charging, downloadinginformation, uploading information, or playing media, or connection isidle).

The docking context can also include other factors related to theconnection between the client device 102 and the docking station 106,such as the length of time the client device 102 and the docking station106 have been connected. The docking context can include one or morecapabilities of the docking station 106 (e.g., GPS receiver, visualdisplay, audio output, and network access). The docking context can alsoinclude one or more identifiers that indicate a model, manufacturer, andsoftware version of the docking station 106. The docking context canalso include the factors described above for multiple devices, includingperipheral devices connected to the client device 102 (e.g., printers,external storage devices, and imaging devices).

In some implementations, the docking context indicates information aboutdocking stations that are physically coupled to the client device, forexample, through a cable or a direct physical link. In someimplementations, the docking context indicates docking stations 106 thatare determined to be in geographical proximity to the client device 102and are connected through a wireless protocol such as Bluetooth. Forexample, when the client device 102 is in a vehicle, the client device102 may wirelessly connect to a docking station 106 that is physicallyconnected to the vehicle. Even if the client device 102 is notphysically connected to the vehicle docking station 106, the wirelessconnection can be included in the docking context. As another example,the docking context can indicate one or more other devices incommunication with the client device 102, such as a wirelessly connectedearpiece. The docking context can include any of the devices with whichthe client device 102 is in communication.

The client device 102 generates docking context information 107 thatindicates one or more aspects of the docking context. The dockingcontext information 107 is associated with the audio data 105. Forexample, the docking context information 107 can indicate the dockingcontext of the client device 102 in which the speech encoded in theaudio data 105 was detected by the client device 102. The client device102 or another system can store the docking context information 107 inassociation with the audio data 105.

During state (B), the speech recognition system 104 accesses the dockingcontext information 107. The speech recognition system 104 also accessesthe audio data 105. For example, the client device 102 can transmit thedocking context information 107 and the audio data 105 to the speechrecognition system 104. Additionally, or alternatively, the dockingcontext information 107, the audio data 105, or both can be accessedfrom a storage device connected to the speech recognition system 104 orfrom another system.

In some implementations, the docking context information 107 can beaccessed before the audio data 105, or even before the terms 103 encodedin the audio data 105 are spoken. For example, the client device 102 canbe configured to provide updated docking context information 107 to thespeech recognition system 104 when the docking context of the clientdevice 102 changes. As a result, the most recently received dockingcontext information 107 can be assumed to indicate the current dockingcontext. The speech recognition system 104 can use the docking contextinformation 107 to select a language model to use to recognize the firstword in a speech sequence. In some implementations, the speechrecognition system 104 can select the language model based on thedocking context information 107 even before the user 101 begins tospeak.

During state (C), the speech recognition system 104 identifies multiplelanguage models 111 a-111 d. The language models 111 a-111 d canindicate, for example, a probability of an occurrence of a term in asequence of terms based on other terms in the sequence. Language modelsand how they can be used are described in greater detail with referenceto FIGS. 2A and 2B.

The language models 111 a-111 d can each be separately focused on aparticular topic (e.g., navigation or shopping) or type of terms (e.g.,names or addresses). In some instances, language models 111 a-111 d canbe specialized for a specific action (e.g., voice dialing or playingmedia) or for a particular docking context (e.g., undocked, connected toa car docking station, or connected to a media docking station). As aresult, the language models 111 a-111 d can include a subset of thevocabulary included in a general-purpose language model. For example,the language model 111 a for navigation can include terms that are usedin navigation, such as numbers and addresses.

The speech recognition system can identify even more fine-grainedlanguage models than those illustrated. For example, instead of a singlelanguage model 111 d for media, the speech recognition system 104 canidentify distinct language models (or portions of the language model 111d) that relate to video, audio, or images.

In some implementations, the language models 111 a-111 d identified canbe submodels included in a larger, general language model. A generallanguage model can include several language models trained specificallyfor accurate prediction of particular types of words. For example, onelanguage model may be trained to predict names, another to predictnumbers, and another to predict addresses, and so on.

The speech recognition system 104 can identify language models 111 a-111d that are associated with the docking context indicated in the dockingcontext information 107. For example, the speech recognition system 104can identify language models 111 a-111 d that have at least a thresholdprobability of matching terms 103 spoken by the user 101. As anotherexample, a particular set of language models 111 a-111 d can bepredetermined to correspond to particular docking context.

Additionally, or alternatively, the speech recognition system 104 canidentify language models 111 a-111 d based on previously recognizedspeech. For example, the speech recognition system 104 may determinethat based on a prior recognized word, “play”, a language model forgames and a language model for media are the most likely to match termsthat follow in the sequence. As a result, the speech recognition system104 can identify the language model for games and the language model formedia as language models that may be used to recognize speech encoded inthe audio data 105.

During state (D), the speech recognition system 104 determines weightingvalues for each of the identified language models 111 a-111 d based onthe docking context indicated in the docking context information 107. Insome implementations, weighting values for each of the identifiedlanguage models 111 a-111 d are also based on other information, such asoutput from a language model based on already recognized terms in aspeech sequence. The weighting values that are determined are assignedto the respective of the language models 111 a-111 d.

The weighting values can indicate the probabilities that the terms 103spoken by the user 101 match the types of terms included in therespective language models 111 a-111 d, and thus that the languagemodels 111 a-111 d will indicate a correct transcription of the terms103. For example, the weighting value assigned to the navigationlanguage model 111 a can indicate a probability that the speech encodedin the audio data 105 includes navigational terms. The weighting valueassigned to the web search language model 111 b can indicate aprobability that the speech encoded in the audio data includes commonterms generally used in web searches.

In some implementations, the speech recognition system 104 can selectfrom among multiple sets 112, 113, 114, 115 of stored weighting values.Each set 112, 113, 114, 115 of weighting values can correspond to aparticular docking context. In the example illustrated, the set 113 ofweighting values corresponds to the vehicle docking station 106. Becausethe docking context information 107 indicates that the client device 102is connected to a vehicle docking station 106, the speech recognitionsystem selects the set 113 of weighting values corresponding to avehicle docking station 106. The weighting values within the set 113 areassigned to the respective language models 111 a-111 d.

The weighting values in various sets 112, 113, 114, 115 can bedetermined by, for example, performing statistical analysis on a largenumber of terms spoken by various users in various docking contexts. Theweighting value for a particular language model given a particulardocking context can be based on the observed frequency that the languagemodel yields accurate results in that docking context. If, for example,the navigation language model 111 a predicts speech correctly for 50% ofspeech that occurs when a client device 102 is in a vehicle dockingstation, then the weighting value for the navigation language model 111a in the set 113 can be 0.5. An example of how a language model predictsspeech is described below with reference to FIGS. 2A and 2B.

In some implementations, the speech recognition system 104 can determineweighting values for the language models 111 a-111 d by adjusting aninitial set of weighting values. For example, a set 112 of weightingvalues can be used when the docking context information 107 indicatesthat the client device 102 is undocked, or when the docking context ofthe client device 102 is unknown. When docking context information 107indicates the client device 102 is docked, individual weighting valuesof the set 112 can be changed based on various aspects of the dockingcontext. Weighting values can be determined using formulas, look-uptables, and other methods. In some implementations, the speechrecognition system 104 can use docking context to select from among setsof stored weighting values that each correspond to a key phrase. Thesets 112, 113, 114, 115 of weighting values are not required to beassociated directly to a single docking context. For example, the set112 may be associated with the key phrase “navigate to.” When the user101 speaks the terms “navigate to,” the set 112 is selected whether thedocking context is known or not. Also, when the client device 102 isknown to be in the vehicle docking station 106, the set 112 can beselected as if the user had spoken the key phrase “navigate to,” even ifthe user 101 did not speak the key phrase.

Docking context can influence various determinations and types ofweighting values that are ultimately used to select a language model,such as from a start state to a state associated with one or more keyphrases, or from weighting values associated with a key phrase to theselection of a particular language model. Docking context can be used todetermine weighting values used to select one or more statescorresponding to key phrases, and the states corresponding to keyphrases can in turn be associated with weighting values for languagemodels 111 a-111 d. For example, the vehicle docking context can be usedto determine a weighting value of “0.6” for a state corresponding to thephrase “navigate to” and a weighting value of “0.4” for a statecorresponding to the phrase “call.” Each key phrase state can beassociated with a set of weighting values that indicates the likelihoodof various language models from that state.

Even after a state corresponding to a key phrase has been selected, andthe set of weighting values indicating the probabilities of variouslanguage models 111 a-111 d has been selected, docking context can beused to modify the weighting values. For example, a state associatedwith the phrase “navigate to” may include weighting values that indicatethat a navigation language model is twice as likely as a businesslanguage model. The docking context can be used to modify the weightingvalues so that, for recognition of the current dictation, the navigationlanguage model is three times as likely as the business language model.

During state (E), the speech recognition system 104 selects a languagemodel based on the assigned weighting values. As illustrated in table116, weighting values 113 a-113 d from the set 113 are assigned to thelanguage models 111 a-111 d. These weighting values 113 a-113 d indicatethe probability that the corresponding language models 111 a-111 d matchthe terms 103 spoken by the user 101, based on the docking contextindicated in the docking context information 107. The language model 111a for navigation has the highest weighting value 113 a, which indicatesthat, based on the docking context, the language model 111 a is the mostlikely to accurately predict the contents of the terms 103 encoded inthe audio data 105. Based on the weighting values, the speechrecognition system 104 selects the language model 111 a to use forspeech recognition of the audio data 105.

In some implementations, a single language model 111 a is selected basedon the weighting values 113 a-113 d. In some implementations, multiplelanguage models 111 a-111 d can be selected based on the weightingvalues 113 a-113 d. For example, a subset including the top N languagemodels 111 a-111 d can be selected and later used to identify candidatetranscriptions for the audio data 105.

The speech recognition system 104 can also select a language model usingthe weighting values in combination with other factors. For example, thespeech recognition system 104 can determine a weighted combination ofthe weighting values 113 a-113 d and other weighting values, such asweighting values based on previous words recognized in the speechsequence or based on previous transcriptions.

As an example, the speech recognition system 104 may transcribe a firstterm in a sequence as “play.” Weighting values based on the dockingcontext alone may indicate that either a navigation language model or amedia language model should be used to recognize subsequent speech. Asecond set of weighting values based on other information (such as theoutput of a language model that was previously used to recognize thefirst term, “play”) may indicate that either a game language model or amedia language model should be used. Taking into account both sets ofweighting values, the speech recognition system 104 can select the medialanguage model as the most likely to yield an accurate transcription ofthe next term in the sequence. As described in this example, in someinstances, different language models can be used to recognize differentterms in a sequence, even though the docking context may be the same foreach term in a sequence.

During state (F), the speech recognition system 104 performs speechrecognition on the audio data 105 using the selected language model 111a. The speech recognition system 104 identifies a transcription for atleast a portion of the audio data 105. The speech recognition system 104is more likely to correctly recognize the terms 103 using the selectedlanguage model 111 a than with a general language model. This is becausethe docking context indicates the types of terms most likely to beencoded in the audio data 105, and the selected language model 111 a isselected to best predict those likely terms.

By using the selected language model 111 a, the speech recognitionsystem 104 may narrow the range of possible transcriptions for the term103 to those indicated by the selected language model 111 a. This cansubstantially improve speech recognition, especially for the first wordin a phrase. Generally, there is a very large set of terms that canoccur at the beginning of a speech sequence. For the first term in thesequence, the speech recognition system does not have the benefit ofprior words in the sequence to indicate terms that are likely to follow.Nevertheless, even with the absence of prior terms that indicate a topic(e.g., “driving directions to” or “show map at”), the speech recognitionsystem 104 still biases recognition to the correct set of terms becausethe selected language model 111 a, selected based on the dockingcontext, is already tailored to the likely content of the terms 103.Using the language model selected based on docking context can thusallow speech recognition as accurate or even more accurate than if theuser had specified the topic of speech in a prefix phrase.

For the same reasons, speech recognition can be improved for singleterms and for short sequences of terms, in which there are fewinterrelationships between words to guide speech recognition. Becausesearch queries often include short sequences of terms, using a languagemodel based on docking context can improve accuracy significantly inthis application.

In the example, the spoken terms 103 include an address, “10 MainStreet,” and there is no spoken prefix phrase (e.g., “navigate to”) thatindicates that the terms 103 include an address. Still, based on thedocking context in which the terms 103 were spoken, the speechrecognition system 104 selects a specialized language model 111 a thatis trained (e.g., optimized or specialized) for addresses. This languagemodel 111 a can indicate a high probability that the first term encodedin the audio data 105 will be a number, and that the first term is thenfollowed by a street name. The specialized vocabulary and patternsincluded in the selected language model 111 a can increase the accuracyof the speech recognition of the audio data 105. For example, terms thatare outside the focus of the selected language model 111 a (e.g., termsunrelated to navigation) can be excluded from the language model 111 a,thus excluding them as possible transcriptions for the terms 103. Bycontrast, those terms may be included as valid transcriptionpossibilities in a general language model, which may include many termsthat seem to be valid possibilities, but are in fact extraneous forrecognizing the current terms 103.

Using the selected language model, the speech recognition system 104selects a transcription, “10 Main Street,” for the audio data 105. Thetranscription can be transmitted to the search engine system 109. Thetranscription can also be transmitted to the client device 102, allowingthe user 101 can verify the accuracy of the transcription and makecorrections if necessary.

During state (G), the search engine system 109 performs a search usingthe transcription of the spoken query terms 103. The search can be a websearch, a search for navigation directions, or another type of search.Information indicating the results of the search query is transmitted tothe client device 102. The transcription is determined using aspecialized language model 111 a that is selected based on the dockingcontext. Accordingly, the likelihood that the transcription matches thequery terms 103 spoken by the user 101 is greater than a likelihoodusing a general language model. As a result, the search query thatincludes the transcription is more likely to be the search that the user101 intended.

Although the transcription of the terms 103 is described as being usedin a search, various other uses of the transcription are possible. Inother implementations, the transcription can be used to, for example,retrieve a map or directions, find and play music or other media,identify a contact and initiate communication, select and launch anapplication, locate and open a document, activate functionality of themobile device 102 (such as a camera), and so on. For each of these uses,information retrieved using the transcription can be identified by oneor more of a server system, the client device 102, or the dockingstation 106.

In some implementations, a different language model 111 a-111 d can beselected and used to recognize speech in different portions of the audiodata 105. Even when the audio data 105 is associated with a singledocking context, other information (such as other recognized words in asequence) can affect the selection of a language model 111 a-111 d. As aresult, different terms in a sequence can be recognized using differentlanguage models 111 a-111 d.

FIG. 2A is a diagram illustrating an example of a representation of alanguage model 200. In general, a speech recognition system receivesaudio data that includes speech and outputs one or more transcriptionsthat best match the audio data. The speech recognition system cansimultaneously or sequentially perform multiple functions to recognizeone or more terms from the audio data. For example, the speechrecognition system can include an acoustic model and a language model200. The language model 200 and acoustic model can be used together toselect one or more transcriptions of the speech in the audio data.

The acoustic model can be used to identify terms that match a portion ofaudio data. For a particular portion of audio data, the acoustic modelcan output terms that match various aspects of the audio data and aweighting value or confidence score that indicates the degree that eachterm matches the audio data.

The language model 200 can include information about the relationshipsbetween terms in speech patterns. For example, the language model 200can include information about sequences of terms that are commonly usedand sequences that comply with grammar rules and other languageconventions. The language model 200 can be used to indicate theprobability of the occurrence of a term in a speech sequence based onone or more other terms in the sequence. For example, the language model200 can identify which word has the highest probability of occurring ata particular part of a sequence of words based on the preceding words inthe sequence.

The language model 200 includes a set of nodes 201 a-201 i andtransitions 202 a-202 h between the nodes 201 a-201 i. Each node 201a-201 i represents a decision point at which a single term (such as aword) is selected in a speech sequence. Each transition 202 a-202 houtward from a node 201 a-201 i is associated with a term that can beselected as a component of the sequence. Each transition 202 a-202 h isalso associated with a weighting value that indicates, for example, theprobability that the term associated with the transition 202 a-202 hoccurs at that point in the sequence. The weighting values can be setbased on the multiple previous terms in the sequence. For example, thetransitions at each node and the weighting values for the transitionscan be determined on the N terms that occur prior to the node in thespeech sequence.

As an example, a first node 201 a that represents a decision point atwhich the first term in a speech sequence is selected. The onlytransition from node 201 a is transition 202 a, which is associated withthe term “the.” Following the transition 202 a signifies selecting theterm “the” as the first term in the speech sequence, which leads to thenext decision at node 201 b.

At the node 201 b there are two possible transitions: (1) the transition202 b, which is associated with the term “hat” and has a weighting valueof 0.6; and (2) the transition 202 c, which is associated with the term“hats” and has a weighting value of 0.4. The transition 202 b has ahigher weighting value than the transition 202 c, indicating that theterm “hat” is more likely to occur at this point of the speech sequencethan the term “hats.” By selecting the transition 202 a-202 h that hasthe highest weighting value at each node 201 a-201 i, a path 204 iscreated that indicates the most likely sequence of terms, in thisexample, “the hat is black.”

The weighting values of transitions in the language model can bedetermined based on language patterns in a corpus of example text thatdemonstrates valid sequences of terms. One or more of the followingtechniques can be used. Machine learning techniques such asdiscriminative training can be used to set probabilities of transitionsusing Hidden Markov Models (“HMMs”). Weighted finite-state transducerscan be used to manually specify and build the grammar model. N-gramsmoothing can be used to count occurrences of n-grams in a corpus ofexample phrases and to derive transition probabilities from thosecounts. Expectation-maximization techniques, such as the Baum-Welchalgorithm, can be used to set the probabilities in HMMs using the corpusof example text.

FIG. 2B is a diagram illustrating an example of a use of an acousticmodel with the language model illustrated in FIG. 2A. The output of thelanguage model can be combined with output of the acoustic model toselect a transcription for audio data. For example, FIG. 2B illustratesthe combination of the output from the acoustic model and the languagemodel for the portion of audio data that corresponds to a single term.In particular, FIG. 2B illustrates the output for audio data thatcorresponds to the term selected by a transition 202 f-202 h from thenode 201 d in FIG. 2A. The language model outputs the terms 212 a-212 cand corresponding weighting values 213 a-213 c that are associated withthe highest-weighted transitions from the node 201 d. The acoustic modeloutputs the terms 216 a-216 c that best match the audio data, withcorresponding weighting values 217 a-217 c that indicate the degree thatthe terms 216 a-216 c match the audio data.

The weighting values 213 a-213 c and 217 a-217 c are combined togenerate combined weighting values 223 a-223 e, which are used to rank acombined set of terms 222 a-222 e. As illustrated, based on the outputof the acoustic model and the language model, the term 222 a “black” hasthe highest combined weighting value 223 a and is thus the most likelytranscription for the corresponding portion of audio data. Although theweighting values 213 a-213 c, 217 a-217 c output by the acoustic modeland language model are shown to have equal influence in determining thecombined weighting values 223 a-223 e, the weighting values 213 a-213 c,217 a-217 c can also be combined unequally and can be combined withother types of data.

FIG. 3 is a flow diagram illustrating an example of a process 300 forperforming speech recognition using a docking context of a clientdevice. Briefly, the process 300 includes accessing audio data thatincludes encoded speech. Information that indicates a docking context ofa client device is accessed. Multiple language models are identified. Atleast one of the language models is selected based on the dockingcontext. Speech recognition is performed on the audio data using theselected language model.

In greater detail, audio data that includes encoded speech is accessed(302). The audio data can be received from a client device. The encodedspeech can be speech detected by the client device, such as speechrecorded by the client device. The encoded speech can include one ormore spoken query terms.

Information that indicates a docking context of a client device isaccessed (304). The docking context can be associated with the audiodata. The information that indicates a docking context can be receivedfrom a client device. For example, the information that indicates adocking context can indicate whether the client device was connected toa docking station while the speech encoded in the audio data wasdetected by the client device. The information that indicates a dockingcontext can also indicate a type of docking station to which the clientdevice was connected while the speech encoded in the audio data wasdetected by the client device.

The information that indicates a docking context can indicate aconnection between the client device and a second device with which theclient device is wirelessly connected. The information that indicates adocking context can indicate a connection between the client device anda second device with which the client device is physically connected.

Multiple language models are identified (306). Each of the multiplelanguage models can indicate a probability of an occurrence of a term ina sequence of terms based on other terms in the sequence. Each of themultiple language models can be trained for a particular topicalcategory of words. The topical categories of words can be different foreach language model. One or more of the multiple language models caninclude a portion of or subset of a language model. For example, one ormore of the multiple language models can be a submodel of anotherlanguage model.

At least one of the identified language models is selected based on thedocking context (308). For example, a weighting value for each of theidentified language models can be determined based on the dockingcontext. The weighting values can be assigned to the respective languagemodels. Each weighting value can indicate a probability that thelanguage model to which it is assigned will indicate a correcttranscription the encoded speech. Determining weighting values for eachof the language models can include accessing stored weighting valuesassociated with the docking context. Determining weighting values foreach of the language models can include accessing stored weightingvalues and altering the stored weighting values based on the dockingcontext.

Determining a weighting value based on the docking context can include,for example, determining that the client device is connected to avehicle docking station, and determining, for a navigation languagemodel trained to output addresses, a weighting value that increases theprobability that the navigation language model is selected relative tothe other identified language models.

Speech recognition is performed on the audio data using the selectedlanguage model (310). A transcription is identified for at least aportion of the audio data. For example, a transcription for one or morespoken terms encoded in the audio data can be generated.

The encoded speech in the audio data can include spoken query terms, andthe transcription of a portion of the audio data can include atranscription of the spoken query terms. The process 300 can includecausing a search engine to perform a search using a transcription of oneor more spoken query terms and providing information identifying theresults of the search query to the client device.

FIG. 4 is a block diagram of computing devices 400, 450 that may be usedto implement the systems and methods described in this document, aseither a client or as a server or plurality of servers. Computing device400 is intended to represent various forms of digital computers, such aslaptops, desktops, workstations, personal digital assistants, servers,blade servers, mainframes, and other appropriate computers. Computingdevice 450 is intended to represent various forms of client devices,such as personal digital assistants, cellular telephones, smartphones,and other similar computing devices. The components shown here, theirconnections and relationships, and their functions, are meant to beexemplary only, and are not meant to limit implementations of theinventions described and/or claimed in this document.

Computing device 400 includes a processor 402, memory 404, a storagedevice 406, a high-speed interface controller 408 connecting to memory404 and high-speed expansion ports 410, and a low speed interfacecontroller 412 connecting to a low-speed expansion port 414 and storagedevice 406. Each of the components 402, 404, 406, 408, 410, and 412, areinterconnected using various busses, and may be mounted on a commonmotherboard or in other manners as appropriate. The processor 402 canprocess instructions for execution within the computing device 400,including instructions stored in the memory 404 or on the storage device406 to display graphical information for a GUI on an externalinput/output device, such as display 416 coupled to high-speed interface408. In other implementations, multiple processors and/or multiple busesmay be used, as appropriate, along with multiple memories and types ofmemory. Also, multiple computing devices 400 may be connected, with eachdevice providing portions of the necessary operations (e.g., as a serverbank, a group of blade servers, or a multi-processor system).

The memory 404 stores information within the computing device 400. Inone implementation, the memory 404 is a volatile memory unit or units.In another implementation, the memory 404 is a non-volatile memory unitor units. The memory 404 may also be another form of computer-readablemedium, such as a magnetic or optical disk.

The storage device 406 is capable of providing mass storage for thecomputing device 400. In one implementation, the storage device 406 maybe or contain a computer-readable medium, such as a floppy disk device,a hard disk device, an optical disk device, or a tape device, a flashmemory or other similar solid state memory device, or an array ofdevices, including devices in a storage area network or otherconfigurations. A computer program product can be tangibly embodied inan information carrier. The computer program product may also containinstructions that, when executed, perform one or more methods, such asthose described above. The information carrier is a computer- ormachine-readable medium, such as the memory 404, the storage device 406,or memory on processor 402.

Additionally, computing device 400 or 450 can include Universal SerialBus (USB) flash drives. The USB flash drives may store operating systemsand other applications. The USB flash drives can include input/outputcomponents, such as a wireless transmitter or USB connector that may beinserted into a USB port of another computing device.

The high-speed interface controller 408 manages bandwidth-intensiveoperations for the computing device 400, while the low-speed interfacecontroller 412 manages lower bandwidth-intensive operations. Suchallocation of functions is exemplary only. In one implementation, thehigh-speed controller 408 is coupled to memory 404, display 416 (e.g.,through a graphics processor or accelerator), and to high-speedexpansion ports 410, which may accept various expansion cards (notshown). In the implementation, low-speed controller 412 is coupled tostorage device 406 and low-speed expansion port 414. The low-speedexpansion port 414, which may include various communication ports (e.g.,USB, Bluetooth, Ethernet, wireless Ethernet) may be coupled to one ormore input/output devices, such as a keyboard, a pointing device, ascanner, or a networking device such as a switch or router, e.g.,through a network adapter.

The computing device 400 may be implemented in a number of differentforms, as shown in the figure. For example, it may be implemented as astandard server 420, or multiple times in a group of such servers. Itmay also be implemented as part of a rack server system 424. Inaddition, it may be implemented in a personal computer such as a laptopcomputer 422. Alternatively, components from computing device 400 may becombined with other components in a client device (not shown), such asdevice 450. Each of such devices may contain one or more of computingdevices 400, 450, and an entire system may be made up of multiplecomputing devices 400, 450 communicating with each other.

Computing device 450 includes a processor 452, memory 464, aninput/output device such as a display 454, a communication interface466, and a transceiver 468, among other components. The device 450 mayalso be provided with a storage device, such as a microdrive, solidstate storage component, or other device, to provide additional storage.Each of the components 452, 464, 454, 466, and 468, are interconnectedusing various buses, and several of the components may be mounted on acommon motherboard or in other manners as appropriate.

The processor 452 can execute instructions within the computing device450, including instructions stored in the memory 464. The processor maybe implemented as a chipset of chips that include separate and multipleanalog and digital processors. Additionally, the processor may beimplemented using any of a number of architectures. For example, theprocessor 402 may be a CISC (Complex Instruction Set Computers)processor, a RISC (Reduced Instruction Set Computer) processor, or aMISC (Minimal Instruction Set Computer) processor. The processor mayprovide, for example, for coordination of the other components of thedevice 450, such as control of user interfaces, applications run bydevice 450, and wireless communication by device 450.

Processor 452 may communicate with a user through control interface 458and display interface 456 coupled to a display 454. The display 454 maybe, for example, a TFT (Thin-Film-Transistor Liquid Crystal Display)display or an OLED (Organic Light Emitting Diode) display, or otherappropriate display technology. The display interface 456 may compriseappropriate circuitry for driving the display 454 to present graphicaland other information to a user. The control interface 458 may receivecommands from a user and convert them for submission to the processor452. In addition, an external interface 462 may be provide incommunication with processor 452, so as to enable near areacommunication of device 450 with other devices. External interface 462may provide, for example, for wired communication in someimplementations, or for wireless communication in other implementations,and multiple interfaces may also be used.

The memory 464 stores information within the computing device 450. Thememory 464 can be implemented as one or more of a computer-readablemedium or media, a volatile memory unit or units, or a non-volatilememory unit or units. Expansion memory 474 may also be provided andconnected to device 450 through expansion interface 472, which mayinclude, for example, a SIMM (Single In-line Memory Module) cardinterface. Such expansion memory 474 may provide extra storage space fordevice 450, or may also store applications or other information fordevice 450. Specifically, expansion memory 474 may include instructionsto carry out or supplement the processes described above, and mayinclude secure information also. Thus, for example, expansion memory 474may be provide as a security module for device 450, and may beprogrammed with instructions that permit secure use of device 450. Inaddition, secure applications may be provided via the SIMM cards, alongwith additional information, such as placing identifying information onthe SIMM card in a non-hackable manner.

The memory may include, for example, flash memory and/or NVRAM memory,as discussed below. In one implementation, a computer program product istangibly embodied in an information carrier. The computer programproduct contains instructions that, when executed, perform one or moremethods, such as those described above. The information carrier is acomputer- or machine-readable medium, such as the memory 464, expansionmemory 474, or memory on processor 452 that may be received, forexample, over transceiver 468 or external interface 462.

Device 450 may communicate wirelessly through communication interface466, which may include digital signal processing circuitry wherenecessary. Communication interface 466 may provide for communicationsunder various modes or protocols, such as GSM voice calls, SMS, EMS, orMMS messaging, CDMA, TDMA, PDC, WCDMA, CDMA2000, or GPRS, among others.Such communication may occur, for example, through radio-frequencytransceiver 468. In addition, short-range communication may occur, suchas using a Bluetooth, WiFi, or other such transceiver (not shown). Inaddition, GPS (Global Positioning System) receiver module 470 mayprovide additional navigation- and location-related wireless data todevice 450, which may be used as appropriate by applications running ondevice 450.

Device 450 may also communicate audibly using audio codec 460, which mayreceive spoken information from a user and convert it to usable digitalinformation. Audio codec 460 may likewise generate audible sound for auser, such as through a speaker, e.g., in a handset of device 450. Suchsound may include sound from voice telephone calls, may include recordedsound (e.g., voice messages, music files, etc.) and may also includesound generated by applications operating on device 450.

The computing device 450 may be implemented in a number of differentforms, as shown in the figure. For example, it may be implemented as acellular telephone 480. It may also be implemented as part of asmartphone 482, personal digital assistant, or other similar clientdevice.

Various implementations of the systems and techniques described here canbe realized in digital electronic circuitry, integrated circuitry,specially designed ASICs (application specific integrated circuits),computer hardware, firmware, software, and/or combinations thereof.These various implementations can include implementation in one or morecomputer programs that are executable and/or interpretable on aprogrammable system including at least one programmable processor, whichmay be special or general purpose, coupled to receive data andinstructions from, and to transmit data and instructions to, a storagesystem, at least one input device, and at least one output device.

These computer programs (also known as programs, software, softwareapplications or code) include machine instructions for a programmableprocessor, and can be implemented in a high-level procedural and/orobject-oriented programming language, and/or in assembly/machinelanguage. As used herein, the terms “machine-readable medium”“computer-readable medium” refers to any computer program product,apparatus and/or device (e.g., magnetic discs, optical disks, memory,Programmable Logic Devices (PLDs)) used to provide machine instructionsand/or data to a programmable processor, including a machine-readablemedium that receives machine instructions as a machine-readable signal.The term “machine-readable signal” refers to any signal used to providemachine instructions and/or data to a programmable processor.

To provide for interaction with a user, the systems and techniquesdescribed here can be implemented on a computer having a display device(e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor)for displaying information to the user and a keyboard and a pointingdevice (e.g., a mouse or a trackball) by which the user can provideinput to the computer. Other kinds of devices can be used to provide forinteraction with a user as well; for example, feedback provided to theuser can be any form of sensory feedback (e.g., visual feedback,auditory feedback, or tactile feedback); and input from the user can bereceived in any form, including acoustic, speech, or tactile input.

The systems and techniques described here can be implemented in acomputing system that includes a back end component (e.g., as a dataserver), or that includes a middleware component (e.g., an applicationserver), or that includes a front end component (e.g., a client computerhaving a graphical user interface or a Web browser through which a usercan interact with an implementation of the systems and techniquesdescribed here), or any combination of such back end, middleware, orfront end components. The components of the system can be interconnectedby any form or medium of digital data communication (e.g., acommunication network). Examples of communication networks include alocal area network (“LAN”), a wide area network (“WAN”), peer-to-peernetworks (having ad-hoc or static members), grid computinginfrastructures, and the Internet.

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made. For example,various forms of the flows shown above may be used, with stepsre-ordered, added, or removed. Also, although several applications ofproviding incentives for media sharing and methods have been described,it should be recognized that numerous other applications arecontemplated. Accordingly, other implementations are within the scope ofthe following claims.

1. A computer-implemented method, comprising: accessing audio data thatincludes encoded speech; accessing information that indicates a dockingcontext of a client device, the docking context being associated withthe audio data; identifying a plurality of language models; identifyingmultiple sets of weighting values for the plurality of language models,the multiple sets of weighting values comprising at least a first set ofmultiple weighting values that correspond to multiple language models ofthe plurality of language models, the first set of multiple weightingvalues being associated with a first key phrase, wherein the first setof multiple weighting values is used to bias selection of a languagemodel when a user utters the first key phrase, and a second set ofmultiple weighting values that correspond to multiple language models ofthe plurality of language models, the second set of multiple weightingvalues being associated with a second key phrase, the second set ofmultiple weighting values being different from the first set of multipleweighting values, and the second key phrase being different from thefirst key phrase; determining that the docking context indicates dockingof the client device with a docking station of a first type; based ondetermining that the docking context indicates docking of the clientdevice with the docking station of the first type, selecting, from amongthe multiple sets of weighting values, the first set of multipleweighting values associated with the first key phrase; selecting atleast a first language model of the plurality of language models usingthe first set of multiple weighting values associated with the first keyphrase; and performing speech recognition on the audio data using thefirst language model to identify a transcription for a portion of theaudio data.
 2. The computer-implemented method of claim 1, wherein theinformation that indicates a docking context of the client deviceindicates a connection between the client device and a second devicewith which the client device is physically connected.
 3. Thecomputer-implemented method of claim 1, wherein the information thatindicates a docking context of the client device indicates a connectionbetween the client device and a second device with which the clientdevice is wirelessly connected.
 4. The computer-implemented method ofclaim 1, wherein identifying the multiple sets of weighting values forthe plurality of language models comprises identifying multiple sets ofweighting values, each set of weighting values indicating probabilitiesthat the respective language models of the plurality of language modelswill indicate a correct transcription for speech when a key phraseassociated with the set of weighting values occurs in the speech.
 5. Thecomputer-implemented method of claim 1, wherein the speech encoded inthe audio data was detected by the client device, and wherein theinformation that indicates a docking context indicates whether theclient device was connected to a docking station while the speechencoded in the audio data was detected by the client device.
 6. Thecomputer-implemented method of claim 1, wherein the speech encoded inthe audio data was detected by the client device, and wherein theinformation that indicates a docking context indicates a type of dockingstation to which the client device was connected while the speechencoded in the audio data was detected by the client device.
 7. Thecomputer-implemented method of claim 1, wherein the encoded speechincludes one or more spoken query terms, and wherein the transcriptionincludes a transcription of the spoken query terms, and wherein themethod further comprises: causing a search engine to perform a searchusing the transcription of the one or more spoken query terms; andproviding information indicating the results of the search query to theclient device.
 8. The computer-implemented method of claim 1, whereineach of the plurality of language models is trained for a particulartopical category of words.
 9. The computer-implemented method of claim1, wherein: determining that the docking context indicates docking ofthe client device with a docking station of a first type comprisesdetermining that the docking context indicates that the docking stationis a vehicle docking station; and based on determining that the dockingcontext indicates docking of the client device with the docking stationof the first type, selecting, from among the multiple sets of weightingvalues, the first set of multiple weighting values associated with thefirst key phrase comprises: in response to determining that the dockingcontext indicates that the docking station is a vehicle docking station,selecting a set of weighting values that increases the probability thata navigation language model is selected relative to the other languagemodels in the plurality of language models.
 10. The method of claim 1,wherein the first type is selected from a group consisting of a mediaplayer docking station type, a vehicle docking station type, and acomputer docking station type.
 11. The method of claim 1, wherein:determining that the docking context indicates docking of the clientdevice with the docking station of the first type comprises determiningthat the docking station is a vehicle docking station; selecting, fromamong the multiple sets of weighting values, the first set of multipleweighting values associated with the first key phrase comprisesselecting a set of weighting values associated with a key phrase that isassociated with navigation; and selecting at least the first languagemodel of the plurality of language models comprises selecting a languagemodel associated with navigation.
 12. The method of claim 1, wherein:determining that the docking context indicates docking of the clientdevice with the docking station of the first type comprises determiningthat the docking station is a media playing device; selecting, fromamong the multiple sets of weighting values, the first set of multipleweighting values associated with the first key phrase comprisesselecting a set of weighting values associated with a key phrase that isassociated with media; and selecting at least the first language modelof the plurality of language models comprises selecting a language modelassociated with media.
 13. The method of claim 1, wherein: determiningthat the docking context indicates docking of the client device with thedocking station of the first type comprises determining that the dockingstation is a computer; selecting, from among the multiple sets ofweighting values, the first set of multiple weighting values associatedwith the first key phrase comprises selecting a set of weighting valuesassociated with a key phrase that is associated with Internet searching;and selecting at least the first language model of the plurality oflanguage models comprises selecting a language model associated withInternet searching.
 14. The computer-implemented method of claim 1,further comprising: accessing second audio data that includes encodedspeech; accessing information that indicates a second docking context ofthe client device, the second docking context being associated with thesecond audio data; determining that the second docking context indicatesdocking of the client device with a second docking station of a secondtype, the second type being different from the first type; based ondetermining that the second docking context indicates docking of theclient device with the second docking station of the second type,selecting, from among the multiple sets of weighting values, the secondset of multiple weighting values associated with the second key phrase;selecting at least a second language model of the plurality of languagemodels using second set of multiple weighting values associated with thesecond key phrase, the second language model being different from thefirst language model; and performing speech recognition on the secondaudio data using the second language model to identify a transcriptionfor a portion of the second audio data, wherein docking stations of thefirst type provide capabilities for one or more first manners of usingthe client device, and wherein docking stations of the second typeprovide capabilities for one or more second manners of using the clientdevice that are different from the one or more first manners of usingthe client device.
 15. The computer-implemented method of claim 1,wherein identifying multiple sets of weighting values for the pluralityof language models comprises identifying multiple sets of weightingvalues that bias selection of language models, each of the multiple setsof weighting values biasing selection of language models for recognizingutterances in audio input when a key phrase associated with the set ofweighting values is recognized in the audio input.
 16. Thecomputer-implemented method of claim 15, wherein selecting, from amongthe multiple sets of weighting values, the set of weighting valuesassociated with the first key phrase comprises selecting the first setof multiple weighting values based on determining that the first dockingcontext indicates docking of the client device with the first dockingstation of the first type, without recognizing the first key phraseassociated with the first set of multiple weighting values.
 17. Thecomputer-implemented method of claim 1, further comprising: accessingsecond audio data that includes encoded speech; determining that theencoded speech included in the second audio data includes the first keyphrase; based on determining that the encoded speech included in thesecond audio data includes the first key phrase, selecting, from amongthe multiple sets of weighting values, the first set of multipleweighting values associated with the first key phrase; selecting atleast a first language model of the plurality of language models usingthe first set of multiple weighting values associated with the first keyphrase; and performing speech recognition on the second audio data usingthe first language model to identify a transcription for a portion ofthe second audio data.
 18. The computer-implemented method of claim 1,wherein identifying multiple sets of weighting values for the pluralityof language models comprises identifying sets of weighting values thateach comprise a weighting value corresponding to each language model ofthe plurality of language models.
 19. The computer implemented method ofclaim 1, wherein identifying multiple sets of weighting values for theplurality of language models comprises identifying the second set ofmultiple weighting values, wherein the second set of multiple weightingvalues is used to bias selection of a language model when a user uttersthe second key phrase.
 20. A system comprising: one or more processors;and a computer-readable medium coupled to the one or more processorshaving instructions stored thereon which, when executed by the one ormore processors, cause the system to perform operations comprising:accessing audio data that includes encoded speech; accessing informationthat indicates a docking context of a client device, the docking contextbeing associated with the audio data; identifying a plurality oflanguage models; identifying multiple sets of weighting values for theplurality of language models, the multiple sets of weighting valuescomprising at least a first set of multiple weighting values thatcorrespond to multiple language models of the plurality of languagemodels, the first set of multiple weighting values being associated witha first key phrase, wherein the first set of multiple weighting valuesis used to bias selection of a language model when a user utters thefirst key phrase, and a second set of multiple weighting values thatcorrespond to multiple language models of the plurality of languagemodels, the second set of multiple weighting values being associatedwith a second key phrase, the second set of multiple weighting valuesbeing different from the first set of multiple weighting values, and thesecond key phrase being different from the first key phrase; determiningthat the docking context indicates docking of the client device with adocking station of a first type; based on determining that the dockingcontext indicates docking of the client device with the docking stationof the first type, selecting, from among the multiple sets of weightingvalues, the first set of multiple weighting values associated with thefirst key phrase; selecting at least a first language model of theplurality of language models using the first set of multiple weightingvalues associated with the first key phrase; and performing speechrecognition on the audio data using the first language model to identifya transcription for a portion of the audio data.
 21. The system of claim20, wherein identifying the multiple sets of weighting values for theplurality of language models comprises identifying multiple sets ofweighting values, each set of weighting values indicating probabilitiesthat the respective language models of the plurality of language modelswill indicate a correct transcription for speech when a key phraseassociated with the set of weighting values occurs in the speech. 22.The system of claim 20, wherein the speech encoded in the audio data wasdetected by the client device, and wherein the information thatindicates a docking context indicates whether the client device wasconnected to a docking station while the speech encoded in the audiodata was detected by the client device.
 23. The system of claim 20,wherein the speech encoded in the audio data was detected by the clientdevice, and wherein the information that indicates a docking contextindicates a type of docking station to which the client device wasconnected while the speech encoded in the audio data was detected by theclient device.
 24. A non-transitory computer storage medium encoded witha computer program, the program comprising instructions that whenexecuted by one or more computers cause the one or more computers toperform operations comprising: accessing audio data that includesencoded speech; accessing information that indicates a docking contextof a client device, the docking context being associated with the audiodata; identifying a plurality of language models; identifying multiplesets of weighting values for the plurality of language models, themultiple sets of weighting values comprising at least a first set ofmultiple weighting values that correspond to multiple language models ofthe plurality of language models, the first set of multiple weightingvalues being associated with a first key phrase, wherein the first setof multiple weighting values is used to bias selection of a languagemodel when a user utters the first key phrase, and a second set ofmultiple weighting values that correspond to multiple language models ofthe plurality of language models, the second set of multiple weightingvalues being associated with a second key phrase, the second set ofmultiple weighting values being different from the first set of multipleweighting values, and the second key phrase being different from thefirst key phrase; determining that the docking context indicates dockingof the client device with a docking station of a first type; based ondetermining that the docking context indicates docking of the clientdevice with the docking station of the first type, selecting, from amongthe multiple sets of weighting values, the first set of multipleweighting values associated with the first key phrase; selecting atleast a first language model of the plurality of language models usingthe first set of multiple weighting values associated with the first keyphrase; and performing speech recognition on the audio data using thefirst language model to identify a transcription for a portion of theaudio data.
 25. The computer storage medium of claim 24, whereinidentifying the multiple sets of weighting values for the plurality oflanguage models comprises identifying multiple sets of weighting values,each set of weighting values indicating probabilities that therespective language models of the plurality of language models willindicate a correct transcription for speech when a key phrase associatedwith the set of weighting values occurs in the speech.
 26. The computerstorage medium of claim 24, wherein the speech encoded in the audio datawas detected by the client device, and wherein the information thatindicates a docking context indicates whether the client device wasconnected to a docking station while the speech encoded in the audiodata was detected by the client device.
 27. The computer storage mediumof claim 24, wherein the speech encoded in the audio data was detectedby the client device, and wherein the information that indicates adocking context indicates a type of docking station to which the clientdevice was connected while the speech encoded in the audio data wasdetected by the client device.
 28. The computer storage medium of claim24, wherein the encoded speech includes one or more spoken query terms,and wherein the transcription includes a transcription of the spokenquery terms, and wherein the operations further comprise: causing asearch engine to perform a search using the transcription of the one ormore spoken query terms; and providing information indicating theresults of the search query to the client device.